Infection is the leading cause of morbidity and mortality in patients with acute leukemia and a major cause in other types of advanced malignancies. The aims of this project are to catalogue and identify the infections, identify the predisposing factors, and evaluate new techniques for more rapid and/or accurate diagnosis of infection. This program has been in progress for over 5 years and has allowed meaningful evaluation of the types of infection occurring in different types of tumor patients. Further, specific problems have been identified such that appropriate intensive preventive measures could be devised and enforced with consequent marked reduction in infection morbidity.